Manufacture of cellulose derivatives



Patented Apr. 30, 1929.

UNITED STATES HENRY DREYZFUS, OF LONDON, ENGLAND.

MAKUFAGTUBE 0F GELLULOSE DERIVATIVES.

No'Drawing. Application filed October 31, 1925, Serial No. 66,104, and in Great Britain October 6, 1925.

This invention relates to the production of cellulose acetate or other cellulose esters.

In my French Patent No. 565,65a and my U. S. application Serial No. 633016, I have describedinter alia how cellulosic materials may be pretreated with organic acids, such as acetic acid or formic acid or the like at ordi nary or raised temperatures or with cooling, before subjecting them to acctylation or other esterification, while in U. S. application Serial No. 7 47 ,054 and British Patent No. 249,- 173 I have described how such pretreatment with organic acids may be preceded, particularly in the case of cellulosic materials other than cotton such as wood pulps, by a treatment with alkaline substances, to render the materials more reactive to acetylation or other'esterification.

Further in U. S. application Serial No. 66,103 and British Patent No. 263,938 I have described how the pretreatment of the cellulosic materials, whether or not they have been subjected to the alkaline treatment of U. S. application Serial No. 747,054 and British Patent No. 249,17 3, may be carried out with vapors of the organic acids, particularly lower fatty acids such as formic or acetic acid, the vapors being employed alone or in admixture with air or other inert gas or being generated by soaking the materials in the concentrated 0r dilute acids and subsequently pass ing air or other inert gas through the materials. Preferably after the treatment air or other inert gas is passed through the materials to remove the organic acid wholly or partially.

Now in my U. S. application Serial No. 633,016 and my French specification No. 565,654 I have shown that. by using comparatively large quantities of acetic acid in the esterilication, one can reduce very substantially the quantity of sulphuric acid used as condensing agent, as for instance to a minimum quantity such as to 3%.

I have now found that even with reduced quantities of acetic acid, for example 4 to about 6 or 7 times the weight of the cellulose or even less, it is possible to reduce the quantity of sulphuric acid without deleterious eliect when cellulose or cellulosic materials are employed which have previously been submitted to the pretreatment with vapors of organic acids as described in my aforesaid U. S. application Serial No. 66,103 and in my British Patent No. 263,938.

According to the present invention, I acetylate or otherwise esterity ccllulosic materials which have been submitted to the pretreatment processes described in my U. S. application S. No. 633,016 or my said British Patent No. 263,938 or my U. S. application S. No. 66,103 (of even date herewith), the acetylation or other esterification bein performed in the presence of relatively small quantities of acetic acid, for example from 4 to about 6 or 7 times the weight of the cellulosic material or less, and in the presence of small quantities of condensing agents, such as sulphuric acid, e. g. under about 70 to 3% on the weight of the cellulose. I

In performing the present invention I may employ cellulosic materials which have been submitted to any of the pretreatments de scribed in my British Patent No. 263,938 or. my U. S. application S. No. 66,103 (of even date herewith) for example by passing air or other indifferent gases laden with acetic or formic acid vapour (for example for some hours up to 24 hours or more) or by any other of the pretreatments described in my said specifications. The cellulosic materials become so reactive for acetylation or esterification that with relatively very reduced quantities of sulphuric acid they maybe acetylated without cooling or without much cooling, as indicated in my previous British Patent N 0. 207,562 and in my U. S. application S. No. 633,016 e. g. with quantities of: sulphuric acid from about 3% to 70 or even less and at ordinary temperature or even at higher tem perature. V

If desired the acetylation or esterification may be executed in suspension, for instance by treating the said pretreated cellulosic materials with the aforesaid relatively small quantity of condensing agent such as sulphuric acid, and the aforesaid relatively small quantity of acetic acid, the mixture being diluted with benzol and acetic anh dride added.

Further, I have found 't at the acetylation or esterification process of the present invention may with advantage be performed in presence of relatively small quantities, such as about 1% to 10% or more on the weight of the cellulose, of organic products which have a substantially increased solvent power as compared with acetic acid, for the acetylated or esteritied cellulose produced, said organic products preventing or restraining the tend ency of the cellulose derivatives to'precipitate out during the acetylation or other esteritication, which precipitation is believed to be the cause of gelatinization or stiffening.- Such organic products are for example ethylidenc diacetate, lactic acid or its acetyl derivatives, etc. etc. The presence of such organic products prevents thisgelatinization and so enables the production of useful cellulose acetates or esters even though small quantities of condensing agents, such as sulphuric acid, etc. and relatively small quantities of acetic acid, are used. Of these products ethylidene diacetate especially presents the advantage that it may be recovered after the acetylation or esterification, either as acetaldehyde or by oxidizing the acetaldehyde to acetic acid. In the latter case the recovery of the acetic acid thus formedwill lit into the system of recovery of the acetic acid used in the acetylation or esterification, thereby avoiding the difiiculty which has resulted from the formation of new products in the reaction mixture,

' which new products would also have to be eliminated.

For the purpose of the present invention I may employ as cellulosic materials cotton (mercerized or non-mercerized) or wood pulps (preferably wood pulp which has been submitted to treatment with alkali especially such as indicated in my British Patent No. 249,173 and in my U. S. application No.

747,054) or other cellulose materials or con version products which have been submitted to the hereinbefore indicated pretreatments.

The following examples are given by way of illustration, it being understood that they are in no way limitativc.

E trample hours with about 5 to times its weight of 80 to 100% acetic acid. Preferably when formic acid vapours are employed the cellulosic material is subjected to a current of air or like indifferent gas to remove substantially or entirely said acid prior to acetylat-ion or esterification.

After pretreatment the cotton is subjected to acetylation with 4 to 6 or 7 times its weight formed at ordinary temperature, but cool-.

ing may be applied if desired or even slight heating, for example to -40 (1, may be applied.

Ewample 2.

Cellulose acetate isprepared in a manner similar to that indicated in Example 1, there being added, however, to the acetylating mixture to 10% (calculated on the cellulose) of ethylidene diacetate. Or if desired the ethylidene diacetate may be formed in the acetylating mixture itself, for example by adding the equivalent amount of acetaldeliyde which combines with the acetic anhydride in presence of the sulphuric acid to form ethylidene diacetate.

The cellulose acetates or other cellulose esters produced by the process of the present invention may if desired be subjected to any suitable secondary treatments, such for ex ample as those described in my prior British Patents Nos. 207562, 20852/1912, my U. S. Patent Reissue No. 14,338, my application No. 633,016 and my British Patent No. 20977/1911 and my U. S. Patent No. 1,217,- 722. The two latter of which in particular describe in detail processes of further treatment for transforming primary acetylation products into products having other solubilities as desired, and to which I refer for the sake of brevity.

By way of example, the further treatment to vary the solubilities of'the primary esterification products maybe effected by exposing the primary products to the further treatment without isolation from the esterification solir tions, or by isolating the products and expos- 'ing them to the secondary treatment either redissolved or in suspension, it being remen'rbered that in conducting the secondary reaction any excess or remaining anhydride has first to be destroyed by water or other anhydride-destroying agents which should preferably be themselves capable of esterification without producing water, e. g. lactic acid, and that the secondary reaction may proceed in the absence or-in the presence of water or similarly acting agents, and that according to the quantity of water or similarly acting agents used or present in the secondary reaction, and to the time of reaction and temperature observed, different phases of soluqbilities can be reached and disappear again according as the reaction is prolonged, it being understood that the less the amount of water or similarly acting agent usedthe greater will be the range of these phases.

The further treatment or reaction may preferably take place at about ordinary tem perature,-or as explained in my said patents,

in order to quicken the reaction, one may apacetylating ply heat or even in some cases heat up to or even -100 C. (after neutralizing condensing agent that may be present, preferably to the extent of neutral sulphate or neutral sulphate or neutral salt).

It is to be understood, however, that the various solubilities developed in the second ary reaction or treatment of the products of the present invention do not necessarily correspond to those developed in the products obtained according to my said previous British Patents Nos. 20977/1911, Filth/1915, 6-lG3/l5 and 100009, or U. S. Patents Reissue No. 14.338 and Nos. 1,278,885, 1,280,974 and 1,280,975 inasmuch as the primary acetylation products obtainable by the new process of the present invention may have other solubilities than those produced accord ing to my said previous specifications and patents.

Further any other processes of secondary reaction or further treatment may be applied to the primary materification products ob tained according to the present invention.

Vt hat I claim and desire to secure by Letters Patent is:

1. A process for the production of cellulose esters which comprises pretreating cellulosic materials with a gas comprising vapors of a lower fatty acid and then esterifying said pretreated cellulosic materials in the presence of under 3% of condensing agent calculated on thecellulose and in the presence of acetic acid in quantity under six times the weight of the cellulose.

2. A process for the production of cellulose acetates which comprises pretreating cel-' lulosic materials with a gas comprising vapors of acetic acid and then acetylating said pretreated cellulosic materials in the presence of under 3% of condensing agent calculated on the cellulose and in' the presence of acetic acid in quantity under six times the weight of the cellulose.

3. A process for the production of cellulose esters which comprises pretreating.cellulosic materials'with a gas comprising vapors of a lower fatty acid and an inert gas and then esterifying said pretreated cellulosic materials in the presence of under 3% of condensing agent calculated on the cellulose and in the presence of aceticacid in quantity under six times the weight of the cellulose.

4. A process for the production of cellulose acetates which comprises pretreating celv lulosicmaterials with. a gas comprising vapors of acetic acid and an inert gas and then said pretreated cellulosic materials in the presence of under 3% of condensingagent calculated on the cellulose and in the presence of acetic acid in quantity under I six times the weight of the cellulose.

5. A process for the production of cellulose esters which comprises pretreating cellulosic materials wlth a gas comprising vaporsof a lower fatty acid and an inert. gas by first treating the materials with a liquid 'containing the lower fatty acid and then passing the inert gas through the materials to bring the vapors of said acid into contact therewith, and then esterifying said pretreated cellulosic materials in the presence of under 3% of con densing agent calculated on the cellulose and in the presence of acetic acid in quantity under six times the weight of the cellulose.

6. A process for the production of cellulose acetates which comprises pretreating cellulosic materials with a gas con'lprising vapors of acetic acid and an inert gas by first treating the materials with a liquid containing the acetic acid and then passing the inert as thlfough the materials to bring the vapors of said acid into contact therewith, and then acetylating said pretreated cellulosic' materials in the presence of under of condensing agent calculated on the cellulose and in the presence of acetic-acid in quantity under six times the weight of the cellulose.

7. A process for the production of cellulost esters which comprises pretrcating cellulosic materials with a as comprising vapors of a lower fatty acid and then esterifying said pretreated cellulosic materials in the resence of'under 3% condensing agent calcu ated on the cellulose and in the presence of acetic acid in quantities under six times the weight of cellulose, the esterification being effected in thepresence of organic products suitable for the prevention of gelatinization of the cellulose derivatives during esterification.

8. A process for the producting of cellulose acetates which comprises pretreating cellulosic materials with a gas comprising vapors of acetic acid and then acetylating said pretreated materials in the presence of under 3% of condensing agent calculated on the cellulose and inthe presence of acetic acid in quantities under six times the weight of cellulose, the acetylation being effected in the presence of organic products suitable for the prevention of gelatinization of the cellulose derivatives during acetylation.

9. A process for the production of cellulose esters which comprises pretreating cellulosic materials with a gas comprising vapors of a lower fatty acid and then esterifying said pretreated cellulosic materials in the presonce of under 3% of condensing agent calculated on the cellulose and 1n the presence of acetic acid in quantity under six times the weight of the cellulose, the acetylation being effected in the presence of ethylidene diacetate thereby preventing gelatinization of the cellulose derivatives during acetylation.

11. A process for the production of cellulose esters which comprises pretreating cellulosie materials with a gas comprising vapors of a lower fatty acid and then esterit'ying said pretreated cellulosic materials in the presence of under 3% of condensing agent calculated on the cellulose and in the presence of acetic acid in quantity under six times the Weight of the cellulose, the esterification being effected in suspension in the presence of diluents.

12., A process for the production of cellulose acetates which comprises pretreating cellulosic materials with a gas comprising vapors of acetic acid and then acetylating said pretreated cellulosic materials in the presence of under 3% of condensing agent calculated on the cellulose and in the pres ence of acetic acid in uantity under six times the weight of the ce lulose, the acetylation being effected in suspension in the presence of diluents. 13. A process for the production of cellulose esters which comprises pretreating cellulosic materials with a gas comprising vapors of a lower fatty acid and then esterifying said pretreated cellulosic materials in the presence of under 3% of condensing agent calculated on the cellulose and in the presence of acetic acid in quantity under six times the weight of the cellulose the csterification being effected in suspension in the presence of benzol.

14. A process for the production of cellulose acetates which comprises pretreating cellulosic materials with a gas comprising vapors of acetic acid and then acetylating' said pretreated cellulosic materials in the presence of under 3% of condensing agent calculated on the cellulose and in the presence of acetic acid in uantity under six times the weight of the c llulose, the acetylation being effected in suspension in the presence of benzol.

In testimony whereof, I have hereunto subscribed my name.

HENRY DREYFUS. 

